Methods of forming backside self-aligned vias and structures formed thereby

ABSTRACT

Methods and structures formed thereby are described, of forming self-aligned contact structures for microelectronic devices. An embodiment includes forming a trench in a source/drain region of a transistor device disposed in a device layer, wherein the device layer is on a substrate, forming a fill material in the trench, forming a source/drain material on the fill material, forming a first source/drain contact on a first side of the source/drain material, and then forming a second source drain contact on a second side of the source/drain material.

CLAIM FOR PRIORITY

This application is a Continuation of U.S. patent application Ser. No.15/754,804, filed Feb. 23, 2018, titled, “METHODS OF FORMING BACKSIDESELF-ALIGNED VIAS AND STRUCTURES FORMED THEREBY”, which is a NationalStage Entry of, and claims priority to, PCT Patent Application No.PCT/US2015/052033, filed on Sep. 24, 2015 and titled “METHODS OF FORMINGBACKSIDE SELF-ALIGNED VIAS AND STRUCTURES FORMED THEREBY”, which isincorporated by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

Microelectronic devices, such as monolithic integrated circuits (ICs),for example, may include a number of transistors, such as metal oxidesemiconductor field effect transistors (MOSFETs) fabricated over asubstrate, such as a silicon wafer. As device sizes continue todecrease, stacking of devices in a third dimension, typically referredto as vertical scaling, or three-dimensional (3D) integration, becomes apromising path toward greater device density.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming certain embodiments, the advantages of theseembodiments can be more readily ascertained from the followingdescription of the invention when read in conjunction with theaccompanying drawings in which:

FIG. 1 represents a perspective view of a structure according toembodiments.

FIGS. 2a-2p represent side cross sectional views of structures accordingto embodiments

FIG. 3 represents a cross sectional view of a structure according toembodiments.

FIG. 4 represents a flow chart of a method according to embodiments.

FIG. 5 represents an interposer implementing one or more embodiments.

FIG. 6 represents a schematic of a system according to embodiments.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, specificembodiments in which the methods and structures may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the embodiments. It is to be understood that thevarious embodiments, although different, are not necessarily mutuallyexclusive. For example, a particular feature, structure, orcharacteristic described herein, in connection with one embodiment, maybe implemented within other embodiments without departing from thespirit and scope of the embodiments. In addition, it is to be understoodthat the location or arrangement of individual elements within eachdisclosed embodiment may be modified without departing from the spiritand scope of the embodiments. The following detailed description is,therefore, not to be taken in a limiting sense, and the scope of theembodiments is defined only by the appended claims, appropriatelyinterpreted, along with the full range of equivalents to which theclaims are entitled. In the drawings, like numerals may refer to thesame or similar functionality throughout the several views.

Implementations of the embodiments herein may be formed or carried outon a substrate, such as a semiconductor substrate. In oneimplementation, the semiconductor substrate may be a crystallinesubstrate formed using a bulk silicon or a silicon-on-insulatorsubstructure. In other implementations, the semiconductor substrate maybe formed using alternate materials, which may or may not be combinedwith silicon, that include but are not limited to germanium, indiumantimonide, lead telluride, indium arsenide, indium phosphide, galliumarsenide, indium gallium arsenide, gallium antimonide, or othercombinations of group III-V or group IV materials. Although a fewexamples of materials from which the substrate may be formed aredescribed here, any material that may serve as a foundation upon which asemiconductor device may be built falls within the spirit and scope.

A plurality of transistors, such as metal-oxide-semiconductorfield-effect transistors (MOSFET or simply MOS transistors), may befabricated on the substrate such as in device layers as will be notedherein. In various implementations, the MOS transistors may be planartransistors, nonplanar transistors, or a combination of both. Nonplanartransistors include FinFET transistors such as double-gate transistorsand tri-gate transistors, and wrap-around or all-around gate transistorssuch as nanoribbon and nanowire transistors. Although theimplementations described herein may illustrate non-planar transistors,it should be noted that embodiments may also be carried out using anyother suitable type of transistor architecture.

Each transistor may include a gate stack formed of at least two layers,for example, a gate dielectric layer and a gate electrode layer. Thegate dielectric layer may include one layer or a stack of layers. Theone or more layers may include silicon oxide, silicon dioxide (SiO₂)and/or a high-k dielectric material. The high-k dielectric material mayinclude elements such as hafnium, silicon, oxygen, titanium, tantalum,lanthanum, aluminum, zirconium, barium, strontium, yttrium, lead,scandium, niobium, and zinc. Examples of high-k materials that may beused in the gate dielectric layer include, but are not limited to,hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanumaluminum oxide, zirconium oxide, zirconium silicon oxide, tantalumoxide, titanium oxide, barium strontium titanium oxide, barium titaniumoxide, strontium titanium oxide, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, and lead zinc niobate. In some embodiments, anannealing process may be carried out on the gate dielectric layer toimprove its quality when a high-k material is used.

The gate electrode layer may be formed on the gate dielectric layer andmay consist of at least one P-type workfunction metal or N-typeworkfunction metal, depending on whether the transistor is to be a PMOSor an NMOS transistor. In some implementations, the gate electrode layermay consist of a stack of two or more metal layers, where one or moremetal layers are workfunction metal layers and at least one metal layeris a fill metal layer.

For a PMOS transistor, metals that may be used for the gate electrodeinclude, but are not limited to, ruthenium, palladium, platinum, cobalt,nickel, and conductive metal oxides, e.g., ruthenium oxide. A P-typemetal layer will enable the formation of a PMOS gate electrode with aworkfunction that is between about 4.9 eV and about 5.2 eV. For an NMOStransistor, metals that may be used for the gate electrode include, butare not limited to, hafnium, zirconium, titanium, tantalum, aluminum,alloys of these metals, and carbides of these metals such as hafniumcarbide, zirconium carbide, titanium carbide, tantalum carbide, andaluminum carbide. An N-type metal layer will enable the formation of anNMOS gate electrode with a workfunction that is between about 3.9 eV andabout 4.2 eV.

In some implementations, the gate electrode may consist of a “U”-shapedstructure that includes a bottom portion substantially parallel to thesurface of the substrate and two sidewall portions that aresubstantially perpendicular to the top surface of the substrate. Inanother implementation, at least one of the metal layers that form thegate electrode may simply be a planar layer that is substantiallyparallel to the top surface of the substrate and does not includesidewall portions substantially perpendicular to the top surface of thesubstrate. In further implementations, the gate electrode may consist ofa combination of U-shaped structures and planar, non-U-shapedstructures. For example, the gate electrode may consist of one or moreU-shaped metal layers formed atop one or more planar, non-U-shapedlayers.

In some implementations, a pair of sidewall spacers may be formed onopposing sides of the gate stack that bracket the gate stack. Thesidewall spacers may be formed from a material such as silicon nitride,silicon oxide, silicon carbide, silicon nitride doped with carbon, andsilicon oxynitride. Processes for forming sidewall spacers may includedeposition and etching process steps. In an alternate implementation, aplurality of spacer pairs may be used, for instance, two pairs, threepairs, or four pairs of sidewall spacers may be formed on opposing sidesof the gate stack.

Source and drain regions may be formed within the substrate adjacent tothe gate stack of each MOS transistor. The source and drain regions aregenerally formed using either an implantation/diffusion process or anetching/deposition process. In the former process, dopants such asboron, aluminum, antimony, phosphorous, or arsenic may be ion-implantedinto the substrate to form the source and drain regions. An annealingprocess that activates the dopants and causes them to diffuse furtherinto the substrate typically follows the ion implantation process.

In an embodiment, the substrate may first be etched to form recesses atthe locations of the source and drain regions. An epitaxial depositionprocess may then be carried out to fill the recesses with material thatis used to fabricate the source and drain regions. In someimplementations, the source and drain regions may be fabricated using asilicon alloy such as silicon germanium or silicon carbide. In someimplementations the epitaxially deposited silicon alloy may be doped insitu with dopants such as boron, arsenic, or phosphorous. In furtherembodiments, the source and drain regions may be formed using one ormore alternate semiconductor materials such as germanium or a groupIII-V material or alloy. And in further embodiments, one or more layersof metal and/or metal alloys may be used to form the source and drainregions.

One or more interlayer dielectrics (ILD) are deposited over the MOStransistors. The ILD layers may be formed using dielectric materialsknown for their applicability in integrated circuit structures, such aslow-k dielectric materials. Examples of dielectric materials that may beused include, but are not limited to, silicon dioxide (SiO₂), carbondoped oxide (CDO), silicon nitride, organic polymers such asperfluorocyclobutane or polytetrafluoroethylene, fluorosilicate glass(FSG), and organosilicates such as silsesquioxane, siloxane, ororganosilicate glass. The ILD layers may include pores or air gaps tofurther reduce their dielectric constant.

Methods and associated structures of forming microelectronic devicestructures, such as self-aligned via structures, are presented. Thosemethods/structures may include forming a trench in a source/drain regionof a transistor device disposed in a device layer, wherein the devicelayer is on a substrate, forming a fill material in the trench, forminga source/drain material on the fill material, forming a firstsource/drain contact on a first side of the source/drain material, andthen forming a second source drain contact on a second side of thesource/drain material. The self-aligned vias/contacts of the embodimentsherein provide interconnect structures for both above and below a devicelayer, within the footprint of the device. Although embodiments hereindepict examples of a non-planar device, the methods and structuresherein may include any type of transistor/device, such as a planar,trigate, fin-fet, omega gate, gate all around device structures, and maycomprise silicon or any other type of materials, such as III-Vmaterials, for example.

FIG. 1 is a perspective view of a non-planar transistor 100, includingat least one gate formed on at least one transistor fin, which areformed on a microelectronic substrate 102. In an embodiment, themicroelectronic substrate 102 may be a monocrystalline siliconsubstrate. The microelectronic substrate 102 may also be other types ofsubstrates, such as silicon-on-insulator (“SOI”), germanium, galliumarsenide, indium antimonide, lead telluride, indium arsenide, indiumphosphide, gallium arsenide, gallium antimonide, and the like, any ofwhich may be combined with silicon.

The non-planar transistor, shown as a tri-gate transistor, may includeat least one non-planar transistor fin 112. The non-planar transistorfin 112 may have a top surface 114 and a pair of laterally oppositesidewalls, sidewall 116 and opposing sidewall 118, respectively.

As further shown in FIG. 1, at least one non-planar transistor gate 122may be formed over the non-planar transistor fin 112. The non-planartransistor gate 122 may be fabricated by forming a gate dielectric layer124 on or adjacent to the non-planar transistor fin top surface 114 andon or adjacent to the non-planar transistor fin sidewall 116 and theopposing non-planar transistor fin sidewall 118. A gate electrode 126may be formed on or adjacent the gate dielectric layer 124. In oneembodiment of the present disclosure, the non-planar transistor fin 112may run in a direction substantially perpendicular to the non-planartransistor gate 122.

The gate dielectric layer 124 may be formed from any well-known gatedielectric material, including but not limited to silicon dioxide(SiO₂), silicon oxynitride (SiO_(x)N_(y)), silicon nitride (Si₃N₄), andhigh-k dielectric materials such as hafnium oxide, hafnium siliconoxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide,zirconium silicon oxide, tantalum oxide, titanium oxide, bariumstrontium titanium oxide, barium titanium oxide, strontium titaniumoxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, andlead zinc niobate. The gate dielectric layer 124 can be formed bywell-known techniques, such as by conformally depositing a gatedielectric material and then patterning the gate dielectric materialwith well-known photolithography and etching techniques, as will beunderstood to those skilled in the art.

The gate electrode 126 may be formed by various methods, according tothe particular application. A source region and a drain region (notshown in FIG. 1) may be formed in the non-planar transistor fin 112 onopposite sides of the gate electrode 126. In one embodiment, the sourceand drain regions may be formed by doping the non-planar transistor fins112, as will be understood to those skilled in the art. In anotherembodiment, the source and drain regions may be formed by removingpotions of the non-planar transistor fins 112 and replacing theseportions with appropriate material(s) to form the source and drainregions, as will be understood to those skilled in the art. In stillanother embodiment, the source and drain regions may be formed byexitaxially growing doped or undoped strain layers on the fins 112.Other methods or combination of methods, may be utilized to form thesource/drain regions, according to the particular application.

In FIGS. 2a-2p , side cross sectional views of structures and methods offorming self-aligned vias are depicted. FIGS. 2a-2p depict crosssectional views along arrows A-A and B-B of a non-planar device, such asthe non-planar device of FIG. 1. In FIG. 2a , a portion of a device 200,such as a transistor device, is depicted. The device 200 may comprise asubstrate 201, in an embodiment, which may further comprise a portion ofa silicon fin 203. A layer 202 may be disposed on the substrate 200,wherein the layer 202 may comprise a dielectric layer/material, but inother embodiments it may comprise a silicon material. A gate electrode226 may be disposed on the layer 202, and may comprise a gate electrodematerial. The gate electrode 226 may further comprise a gate dielectricmaterial (not shown), disposed between the gate electrode 226 and thelayer 202, as well as between a silicon fin 212 and the gate electrode226. In an embodiment, a pair of gate spacers 206 may be disposed oneither side of the gate electrode 226. The view through B depicts thefin 212 portion of the substrate 200, wherein the gate 226 is disposedon the silicon fin 212 portion of the substrate 200. Source/drainregions 208 are adjacent the gate spacers 206 in an embodiment, but inother embodiments, there may be no gate spacers 206 adjacent the gate226, so that the source/drain regions may be adjacent the gate electrode226, without the intervening gate spacers 206.

In FIGS. 2b-2c , a mask material 210 may be formed on the gate electrode226 and on the fin 201 of the device 200, to define an opening 211 inthe source drain regions 208. Any type of process, such as an etchingprocess, may be utilized to form a deep trench opening 211 in thesource/drain regions 208. The mask material 210 may be removed, and thetrench opening 211, which may comprise a source/drain contact opening211, may comprise a depth 203 of between about 20 nanometers and about500 nanometers, in an embodiment (FIG. 2d ). In an optional embodiment,the trench 211 may be lined with a liner material 217, along a sidewallof the trench 211, in an embodiment (FIG. 2e ). In an embodiment, theliner 217 (it may comprise an insulating material, such as an alumina,silicon nitride, silicon carbide, material, for example. In anembodiment, the trench 211 may not be lined with the liner material 217.

In an embodiment, a fill material 214 may be formed within and/or mayfill the trench 211 (FIG. 2f ). In an embodiment, the fill material 214may be formed within the trench 211 by using a multi-step process,wherein the high aspect trench opening may be filled uniformly. In anembodiment, the fill material 214 may comprise a temporary material,such as a titanium containing material, such as titanium nitride,titanium oxide. In another embodiment, the fill material 214 maycomprise a conductive material such as titanium, cobalt, tungsten,copper, or combinations thereof, and the like. In an embodiment, thefill material 214 may be a permanent portion of the device, and may benon-sacrificial. In an embodiment, the fill material 214 may be locatedbelow a typical source/drain trench depth, for example, the fillmaterial 214 may completely or substantially extend through the layer202. In an embodiment, the fill material 214 may be recessed with anetch process so that the fill material 214 may extend through the layer202. In an embodiment, the fin 212 may be recessed and undercut/removedfrom the substrate 201 (FIG. 2g ).

In an embodiment, source/drain material 218 may be formed on and/or inthe source/drain regions (FIG. 2h ). In an embodiment, the source drainmaterial 218 may comprise an epitaxial material, such as a silicongermanium material, for example. In an embodiment, the source drainmaterial 218 adjacent the gate electrode 226 may be on the material 214.In an embodiment, at least a portion of the source/drain material 218may be directly on the material 214. In an embodiment, a firstsource/drain contact 220 may be coupled with and/or formed on thesource/drain material 218 (FIG. 2i ). In an embodiment, the firstsource/drain contact 220 may comprise a lower source/drain contact 220.

In an embodiment, a carrier wafer may be attached to the device 200 (notshown), and the substrate 201 may be reduced in depth and or removed,from the layer 202 (FIG. 2j ). In an embodiment, a portion of thesubstrate 201 may be removed by utilizing a grinding, wet etch or CMPprocess for example. The mechanical base of the silicon fin 212 may berevealed/exposed, the fill material 214 may be exposed, and the backsurface of the substrate 202 may be exposed. In an embodiment, the baseof the silicon fin(s) 212 may be recessed, wherein an opening 215 isformed (FIG. 2k ). The recess of the silicon fin 212 may reduce subfinleakage, in an embodiment. The recessed silicon fin regions may then befilled with a dielectric material 227, such as a silicon dioxidematerial for example, (FIG. 2l ), and may be polished to smooth out thesurface.

In an embodiment, the dielectric 227 may be patterned and etched to formsource drain contact openings 229 (FIGS. 2m-2n ). In an embodiment, thesource/drain contact openings 229 may comprise deep openings, and maycomprise a depth of about 20 nm to about 300 nm, in an embodiment. In anembodiment, the fill material 214 may be removed. However, in someembodiments, the fill material 214 may remain. In an embodiment, thesource/drain openings 229 may be filled with a conductive material toform a second source/drain contact 230 (FIG. 2o ). In an embodiment, thesecond source/drain contacts 230 may comprise self-aligned backsidevias, and may comprise a height of about 40 nm to about 500 nm, in anembodiment. The second source/drain contacts 230 (as well as the firstsource/drain contacts) may comprise conductive materials such as copper,tungsten, cobalt, and titanium, and may comprise an upper contact 230.

In an embodiment, a first side 219 of the source/drain material 218 maybe in direct contact with the first source/drain contact 220, and asecond side 221 of the source/drain material 218 may be in directcontact with the second source/drain contact 230. In another embodiment,the second side 221 of the source/drain material 218 may be in directcontact with a non-sacrificial fill material 214, and thenon-sacrificial fill material 214 may be in direct contact with thesecond contact 230 (FIG. 2p ). The first side 219 of the source/drainmaterial 218 may be in direct contact with the first source/draincontact 220. In an embodiment, the gate electrode 226 may be adjacent tothe first and second source/drain contacts 220, 230, and may be directlyadjacent in some embodiments. In an embodiment, the first source/draincontact and the second source/drain contact may comprise substantiallydifferent heights, and in another embodiment, the height of one of thefirst source/drain contacts is about twice the height of the other ofthe source/drain contacts.

The ability to route the electrical interconnects above and below atransistor layer provides novel routing and scaling options. Embodimentsherein enable the ability to make electrical connections betweeninterconnect layers above and below transistor layers without increasingthe transistor footprint. The additional depth of the trench openingprovides margin needed to connect to the other side of the device layerwithout electrically connecting the transistor channel region, in anembodiment. In an embodiment, self-aligned source drain contacts gothrough the source drain material and connect to an upper interconnectlayer. The connection is within the footprint of the device.

Referring to FIG. 3, in an embodiment, a device structure 300 maycomprise a plurality of upper interconnect structures 335 and aplurality of lower interconnect structures 325. A device layer 310 maycomprise a plurality of devices 322 that may be coupled to both theupper interconnect structures 335 and the lower interconnect structures325, wherein the upper interconnect structures 335 are located above thedevice layer 310 and the lower interconnect structures 325 are locatedbelow the device layer 310. In one embodiment, devices 322 may compriselow power range, typically fast devices including logic devices such asFinFETs or other reduced form factor devices that can generally bearranged on a device layer at a higher pitch than higher voltage rangedevices. In an embodiment, a first source/drain contact 320 may becoupled with a first side 319 of a source/drain region 318 of one of thedevices 322, and a second source/drain contact 330 may be coupled with asecond side 321 of the source/drain region 318. The source/drain regions318 may be adjacent a gate electrode 326. In an embodiment, the firstand second source/drain contacts 320, 330 may be directly coupled to thesource/drain region 318 of the device 322, similar to the structure ofFIG. 2o . In an embodiment, the devices 332 may comprise devices whichdo not comprise fin structures, such as planar transistor devices, orother types of device structures without a silicon fin. In anembodiment, the first and second source/drain contacts 320, 330 maycomprise a via structure (not shown) between them. In anotherembodiment, the second source/drain contact 330 may be directly coupledwith a fill material (not shown), similar to the structure of FIG. 2p .In an embodiment, the gate electrode 226 may be directly coupled to thesource/drain region 318 of the device 322, similar to the structure ofFIG. 2o . In an embodiment, the devices 332 may comprise devices whichdo not comprise fin structures, such as planar transistor devices, orother types of device structures without a silicon fin. In anembodiment, the first and second source/drain contacts 320, 330 maycomprise a via structure (not shown) between them. In anotherembodiment, the second source/drain contact 330 may be directly coupledwith a fill material (not shown), similar to the structure of FIG. 2 p.

The upper and lower source/drain contacts 330, 320 are coupled with theupper and lower plurality of interconnects 325, 335, respectively. In anembodiment, the device 300 may comprise multi-layers of interconnects,such as a first layer of lower interconnects 327, and a first layer ofupper interconnects 337, and so on. In an embodiment, a source drainregion 318, may be disposed between the first source/drain contact 320and the second source/drain contact 320, and may be directly in contactwith both first and second source/drain contacts, however in otherembodiments there may be intervening layers between the first and secondsource/drain contacts and the source/drain region 318.

In one embodiment, the upper and lower plurality of interconnects 325,335 comprise a copper material and may be patterned as is known in theart. Source/drain contacts 320, 330 disposed between circuit devices maycomprise such materials as tungsten or copper material. The plurality ofupper and lower interconnects, as well as the source/drain contacts maybe insulated from one another and from the devices by dielectricmaterials 303, such as with an oxide 303, for example.

FIG. 4 depicts a method according to embodiments herein. At step 402, adeep source/drain trench opening may be formed through a source/drainregion of a substrate adjacent a gate electrode. At step 404, a fillmaterial may be formed in the deep trench opening. At step 406, asource/drain material may be formed on the fill material, and then afirst source/drain contact material may be formed on a first side of thesource/drain material. At step 408, a second source/drain contactmaterial may be formed on a second side of the source/drain material.

In an embodiment, the structures of the embodiments herein may becoupled with any suitable type of structures capable of providingelectrical communications between a microelectronic device, such as adie, disposed in package structures, and a next-level component to whichthe package structures may be coupled (e.g., a circuit board).

The device structures, and the components thereof, of the embodimentsherein may comprise circuitry elements such as logic circuitry for usein a processor die, for example. Metallization layers and insulatingmaterial may be included in the structures herein, as well as conductivecontacts/bumps that may couple metal layers/interconnects to externaldevices/layers. The structures/devices described in the various figuresherein may comprise portions of a silicon logic die or a memory die, forexample, or any type of suitable microelectronic device/die. In someembodiments the devices may further comprise a plurality of dies, whichmay be stacked upon one another, depending upon the particularembodiment. In an embodiment, the die(s) may be partially or fullyembedded in a package structure.

The various embodiments of the device structures included herein may beused for system on a chip (SOC) products, and may find application insuch devices as smart phones, notebooks, tablets, wearable devices andother electronic mobile devices. In various implementations, the packagestructures may be included in a laptop, a netbook, a notebook, anultrabook, a smartphone, a tablet, a personal digital assistant (PDA),an ultra mobilePC, a mobile phone, a desktop computer, a server, aprinter, a scanner, a monitor, a set-top box, an entertainment controlunit, a digital camera, a portable music player, or a digital videorecorder, and wearable devices. In further implementations, the packagedevices herein may be included in any other electronic devices thatprocess data.

FIG. 5 illustrates a device 500 that includes one or more embodiments ofthe invention. The device 500 may include interposer 501, which maycomprise an intervening substrate used to bridge a first substrate 502to a second substrate 504. The first substrate 402 may be, for instance,an integrated circuit die, and may or may not include embodiments of theself-aligned via described structures herein. The second substrate 504may be, for instance, a memory module, a computer motherboard, oranother integrated circuit die, and may or may not include embodimentsof the self-aligned via described structures herein. Generally, thepurpose of an interposer 501 is to spread a connection to a wider pitchor to reroute a connection to a different connection.

For example, an interposer 501 may couple an integrated circuit die to aball grid array (BGA) 506 that can subsequently be coupled to the secondsubstrate 504. In some embodiments, the first and second substrates502/504 are attached to opposing sides of the interposer 501. In otherembodiments, the first and second substrates 502/504 are attached to thesame side of the interposer 501. And in further embodiments, three ormore substrates are interconnected by way of the interposer 501.

The interposer 501 may be formed of an epoxy resin, afiberglass-reinforced epoxy resin, a ceramic material, or a polymermaterial such as polyimide. In further implementations, the interposermay be formed of alternate rigid or flexible materials that may includethe same materials described above for use in a semiconductor substrate,such as silicon, germanium, and other group III-V and group IVmaterials. The interposer may include metal interconnects 508 and vias510, including but not limited to through-silicon vias (TSVs) 512. Theinterposer 501 may further include embedded devices 514, including bothpassive and active devices. Such devices include, but are not limitedto, capacitors, decoupling capacitors, resistors, inductors, fuses,diodes, transformers, sensors, and electrostatic discharge (ESD)devices. More complex devices such as radio-frequency (RF) devices,power amplifiers, power management devices, antennas, arrays, sensors,and MEMS devices may also be formed on the interposer 501. In accordancewith embodiments, apparatuses or processes disclosed herein may be usedin the fabrication of interposer 501.

FIG. 6 is a schematic of a computing device 600 according to anembodiment. In an embodiment, the computing device 600 houses a board602, such as a motherboard 602 for example. The board 602 may include anumber of components, including but not limited to a processor 604, andan on-die memory 606, that may be communicatively coupled with anintegrated circuit die 603, and at least one communication chip 608. Theprocessor 604 may be physically and electrically coupled to the board602. In some implementations the at least one communication chip 608 maybe physically and electrically coupled to the board 602. In furtherimplementations, the communication chip 606 is part of the processor604.

Depending on its applications, computing device 600 may include othercomponents that may or may not be physically and electrically coupled tothe board 602, and may or may not be communicatively coupled to eachother. These other components include, but are not limited to, volatilememory (e.g., DRAM) 610, non-volatile memory (e.g., ROM) 612, flashmemory (not shown), a graphics processor unit (GPU) 614, a digitalsignal processor (DSP) 616, a crypto processor 642, a chipset 620, anantenna 622, a display 624 such as a touchscreen display, a touchscreencontroller 626, a battery 628, an audio codec (not shown), a video codec(not shown), a global positioning system (GPS) device 629, a compass630, accelerometer, a gyroscope and other inertial sensors 632, aspeaker 634, a camera 636, and a mass storage device (such as hard diskdrive, or solid state drive) 640, compact disk (CD) (not shown), digitalversatile disk (DVD) (not shown), and so forth). These components may beconnected to the system board 602, mounted to the system board, orcombined with any of the other components.

The communication chip 608 enables wireless and/or wired communicationsfor the transfer of data to and from the computing device 600. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 608 may implement anyof a number of wireless or wired standards or protocols, including butnot limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family),IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+,EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, Ethernet derivativesthereof, as well as any other wireless and wired protocols that aredesignated as 3G, 4G, 5G, and beyond. The computing device 600 mayinclude a plurality of communication chips 608. For instance, a firstcommunication chip 608 may be dedicated to shorter range wirelesscommunications such as Wi-Fi and Bluetooth and a second communicationchip 1006 may be dedicated to longer range wireless communications suchas GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others. The term“processor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

In various implementations, the computing device 600 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a wearable device, a mobilephone, a desktop computer, a server, a printer, a scanner, a monitor, aset-top box, an entertainment control unit, a digital camera, a portablemusic player, or a digital video recorder. In further implementations,the computing device 600 may be any other electronic device thatprocesses data.

Embodiments may be implemented as a part of one or more memory chips,controllers, CPUs (Central Processing Unit), microchips or integratedcircuits interconnected using a motherboard, an application specificintegrated circuit (ASIC), and/or a field programmable gate array(FPGA).

Although the foregoing description has specified certain steps andmaterials that may be used in the methods of the embodiments, thoseskilled in the art will appreciate that many modifications andsubstitutions may be made. Accordingly, it is intended that all suchmodifications, alterations, substitutions and additions be considered tofall within the spirit and scope of the embodiments as defined by theappended claims. In addition, the Figures provided herein illustrateonly portions of exemplary microelectronic devices and associatedpackage structures that pertain to the practice of the embodiments. Thusthe embodiments are not limited to the structures described herein.

What is claimed is:
 1. A microelectronic device structure, comprising: afin of semiconductor material, the fin comprising a channel region, anda base below the channel region; a dielectric material adjacent to asidewall of the base; a gate electrode adjacent to a sidewall of thechannel region and over the dielectric material; a drain region adjacentto a first end of the channel region; a first contact to a first side ofthe drain region, the first contact adjacent to the gate electrode; asource region adjacent to a second end of the channel region, oppositethe first end; a second contact to a first side of the source region,the second contact adjacent to the gate electrode; and a third contactadjacent to an end of the base, and in contact with a second side of thesource region or the drain region, opposite the first side of the sourceregion or drain region.
 2. The microelectronic device structure of claim1, wherein: the third contact is in contact with the end of the base,and is separated from the first or second contact by only the sourceregion or drain region.
 3. The microelectronic device structure of claim1, wherein the channel comprises silicon and the source region and thedrain region both comprise at least one of silicon and germanium.
 4. Themicroelectronic device structure of claim 1, wherein the third contactcomprises at least one of copper, tungsten, cobalt, or titanium.
 5. Themicroelectronic device structure of claim 1, further comprising firstinterconnects coupled to the first and second contact, and secondinterconnects coupled to the third contact, wherein the firstinterconnects are on a first side of the fin and the secondinterconnects are on a second side of the fin, opposite the first sideof the fin.
 6. The microelectronic device structure of claim 1, wherein:the first contact and the second contact are separated from a sidewallof the gate electrode by an intervening spacer dielectric material; andthe third contact has a first length from the end of the base that issubstantially equal to a first length of the first or second contactfrom the dielectric spacer material.
 7. The microelectronic devicestructure of claim 6, wherein: the source region and drain region have asecond length, orthogonal to the first length that exceeds a transversewidth of the fin; and the third contact also has a second length thatexceeds the transverse width of the fin.
 8. A microelectronic devicestructure, comprising: a first transistor, comprising: a first fin ofsemiconductor material, the first fin comprising a first channel region,and a first base below the first channel region; a dielectric materialadjacent to a sidewall of the first base; a first gate electrodeadjacent to a sidewall of the first channel region and over thedielectric material; a first source/drain region adjacent to a first endof the first channel region; a first contact to a first side of thefirst source/drain region, the first contact adjacent to the first gateelectrode; a second source/drain region adjacent to a second end of thefirst channel region, opposite the first end of the first channelregion; a second contact to a first side of the second source/drainregion, the second contact adjacent to the first gate electrode; and athird contact adjacent to an end of the first base, and in contact withthe second side of the first source/drain region, opposite the firstside of the first source/drain region; and a second transistor,comprising: a second fin of the semiconductor material, the second fincomprising a second channel region, and a second base below the secondchannel region, wherein a sidewall of the second base is separated fromthe sidewall of the first base by the dielectric material; a second gateelectrode adjacent to a sidewall of the second channel region and overthe dielectric material; a third source/drain region adjacent to a firstend of the second channel region; a fourth contact to a first side ofthe third source/drain region, the fourth contact adjacent to the secondgate electrode; a fourth source/drain region adjacent to a second end ofthe second channel region, opposite the first end of the second channelregion; a fifth contact to a first side of the fourth source/drainregion, the fifth contact adjacent to the second gate electrode; and asixth contact adjacent to an end of the second base, and in contact witha second side of the fourth source/drain region, opposite the first sideof the fourth source/drain region, wherein a sidewall of the thirdcontact is separated from a sidewall of the sixth contact by thedielectric material.
 9. The microelectronic device structure of claim 8,wherein: the third contact is in contact with the end of the first base,and is separated from the first contact by only the first source/drainregion; and the sixth contact is in contact with the end of the secondbase, and is separated from the fifth contact by only the fourthsource/drain region.
 10. The microelectronic device structure of claim8, wherein the first and second channel comprises silicon and the sourceregion and the drain region both comprise at least one of silicon andgermanium.
 11. The microelectronic device structure of claim 8, whereinthe third contact and the sixth contact both comprise at least one ofcopper, tungsten, cobalt, or titanium.
 12. The microelectronic devicestructure of claim 8, further comprising: first interconnects coupled tothe first, second, fourth and fifth contacts, wherein the firstinterconnects are on a first side of the first and second fins; andsecond interconnects coupled to the third and sixth contacts, whereinthe second interconnects are on a second side of the first and secondfins, opposite the first side of the first and second fins.
 13. Themicroelectronic structure of claim 8, wherein: a first vertical heightof the first, second, fourth and fifth contacts is substantially thesame; a second vertical height of the third and sixth contacts issubstantially the same; and the second vertical height is less than thefirst vertical height.
 14. The microelectronic structure of claim 13,wherein the first vertical height is at least twice the second verticalheight.
 15. A system comprising: circuitry comprising themicroelectronic device structure of claim 1; and a DRAM communicativelycoupled to circuitry.
 16. A method of forming a microelectronicstructure, the method comprising: forming a gate electrode over asidewall of a channel region of a device layer comprising asemiconductor material; forming trench in the device layer to a depthbelow the channel region; forming a first contact within the trench;forming a source/drain region in contact with the channel region andover the first contact; forming a second contact to a side of thesource/drain region opposite the first contact.
 17. The method of claim16, further comprising forming a first interconnect layer coupled to thefirst contact on a first side of the device layer, and forming a secondinterconnect layer coupled to the second contact on a second side of thedevice layer, opposite the first side of the device layer.
 18. Themethod of claim 16, wherein forming the source/drain region furthercomprises epitaxially growing a material comprising at least one ofsilicon or germanium after forming the first contact.
 19. The method ofclaim 16, wherein forming the first contact comprises at least partiallybackfilling the trench with a conductive material comprising a metal.20. The method of claim 19, wherein the metal comprises at least one ofcopper, tungsten, cobalt, or titanium.